The use of a snap-ring to provide a transition structure between the top of a cylindrical container and a sealing closure for said container is described in U.S. Pat. No. 6,588,618 issued Jul. 8, 2003 to Christopher Davis and assigned to Letica Corporation of Rochester, Mich. The Davis patent discloses a snap-ring adapted to be permanently secured to the top peripheral edge of a molded plastic container by welding or adhesive bonding. After the snap-ring is essentially permanently secured to the container, a closure of suitable design may be removably attached to the snap-ring to seal the container and the contents thereof. This design provides an effective substitute for metal paint cans with conventional lids.
Transition rings which do not require welding or bonding but can be snapped onto a container are known. An example is shown in U.S. Pat. No. 4,356,930, issued to Roper on Nov. 2, 1982. The Roper ring, called an “engagement ring,” snaps into the upper edge of a container sidewall having an undercut and provides an inboard upward annular projection to receive a lid.
The Roper engagement ring depends entirely on the fit between the top edge of the container and an inverted u-shaped slot in the engagement ring to transfer vertical stacking loads from the lid or ring to the container sidewall. This creates the potential for distortion of the ring under load and a loss of seal quality around the top of the container.